Detainees in a holding area at Guantanamo Bay. Photograph: Shane T McCoy/AFP/Getty Images

An inquiry by the US justice department last night reprimanded two senior Bush era lawyers who approved the use of torture at Guantánamo Bay. The department found the two lawyers, John Yoo and Jay Bybee, guilty of poor judgment but not professional misconduct.

The lawyers wrote controversial memorandums dating from 2002 after the 9/11 attacks that provided legal cover for the CIA to use torture and other harsh interrogation techniques. The conclusion of the report, which marks a significant softening of the original draft, will disappoint human rights organisations. Publication of the report has been delayed for months amid fierce internal debate. If the two had been found guilty of professional misconduct, it would have had consequences for their immediate careers and opened the way for legal challenges.

The techniques approved by the lawyers included waterboarding, which Barack Obama has described as torture but the former vice-president, Dick Cheney, insisted was not. Detainees accused of the 9/11 attacks such as Khalid Sheikh Mohammed were repeatedly subjected to waterboarding. Harsh techniques were used against others picked up in Afghanistan and Pakistan and taken to Guantánamo.

The assistant attorney-general, Ronald Weich, found the two lawyers "exercised poor judgment in connection with the drafting of the pertinent memoranda". No disciplinary action is to be taken.

Weich said poor judgment "differs from professional misconduct in that an attorney may act inappropriately and thus exhibit poor judgment even though he or she may not have violated or acted in reckless disregard of a clear obligation or standard". Yoo is a law professor at the University of California at Berkeley and Bybee is a federal appeals court judge.

The Obama administration is reluctant to reopen the row over waterboarding and Obama last year ruled against prosecution of CIA agents involved in torture techniques. He said it was a "time for reflection, not retribution".Other techniques that were approved included walling (in which the suspect could be pushed into a wall), wall standing, and sleep deprivation.